The onset of retinal vascular disease is often subtle and accompanied by sub-clinical signs and symptoms. In the past decade fluoroscein angiography has greatly enhanced knowledge of the pathophysiology of some of these diseases and has aided in the evolution of new methods of treatment (e.g. laser photocoagulation following the NEI-funded diabetic retinopathy study) which significantly reduce the risk of blindness. Diagnosis, prognosis, and evaluation of treatment are limited by the insensitivity of existing clinical methods of assessing vision, which rely predominantly on the Snellen chart measure of visual acuity. Further, the understanding of retinal vascular disease depends on more quantitative measures of blood flow in the retinal by direct measurement techniques such as 2 point-fluorophotometry or laser-doppler velocimetry. The proposed project utilizes sensitive psychophysical tests of vision (color vision, spatial modulation sensitivity, temporal modulation sensitivity and glare recovery), quantitative measures of retinal blood flow (2 point-fluorophotometry), and standard clinical measures of fundus fluoroscein angiography and fundus color photography in the assessment of the natural history of diabetic retinopathy and venous occlusive retinopathy. Psychophysical tests of vision and retinal blood flow measures will be determined on (1) Two vascular disease patient groups -- diabetic retinopathy and venous occlusive retinopathy; (2) Two patient groups predisposed to the above vascular diseases and age-matched to that group -- diabetics of long-standing without retinopathy and systemic hypertensives; (3) A normal patient group, age-matched for the retinal disease groups. The study is intended to identify those vision and retinal blood flow parameters which could most appropriately be used in a follow-on randomized clinical trial to evaluate the efficacy of treatment.